Conventionally, in radar devices, suppressing a signal level of clutters (unnecessary signals) by performing CFAR (Constant False Alarm Rate) processing or scan-to-scan correlation processing is known.
Although an echo from a target object is detected so as to be comparatively stable with time, the signal level of clutters varies at random with time. For this reason, the clutters can be suppressed by performing the scan-to-scan correlation processing for suppressing the signal varying at random with time, leaving the echo from the target object. A radar device for performing the scan-to-scan correlation processing is disclosed in the following publications, for example.
JPA 2003-315439 discloses a configuration including a correlation processing memory that independently stores moving target objects, respectively, and for performing surface correlation processing for every correlation processing memory (scan-to-scan correlation processing). Therefore, this related art can accurately discriminate moving target objects while removing noises, such as sea surface reflections.
JPA H08-136641 discloses a configuration including a recursive digital filter, and for changing and setting a filter characteristic in real time according to a change in echo signal. Therefore, this related art can prevent a target object signal from being suppressed when suppressing a clutter signal.
However, JPA 2003-315439 must provide a memory for every moving target object. For this reason, if the scan-to-scan correlation processing is performed for many target objects, a required memory capacity will be enormous. In addition, there is a problem that a calculation load will also increase.
JPA H08-136641 also determines a rising edge or a trailing edge of the signal, and determines whether the signal is a target object or a clutter. Therefore, complicated processing in which a coefficient of the recursive digital filter is changed based on the determination result must be performed.
JPA 2002-139562 needs to track each moving target object in advance by ARPA (Automatic Collision Prevention Assistance Device) or the like before performing the scan-to-scan correlation processing.
Therefore, there is a problem that the configuration becomes complicated by any of the related arts described above. In addition, the scan-to-scan correlation processing disadvantageously suppresses the echo from the target object which moves at a high speed. For this reason, if the scan-to-scan correlation processing is performed, the echo of the high-speed moving target object is suppressed and, thus, this makes the detection of the high-speed moving target object difficult.